1. Field of the Invention
The present invention relates to a gasket having excellent sealing properties to be disposed at fit-joint-type pipe connection portions of, for example, the exhaust pipe system in a motor vehicle in which a high-temperature gas flows. More specifically, the present invention relates to a spiral wound gasket formed by winding, in the form of a spiral, a metal hoop material and a filler material overlapping each other.
2. Description of the Prior Art
As a gasket to be used for sealing the ends of exhaust pipes in, for example, an internal combustion engine, there is known a gasket as disclosed in Japanese Utility Model Publication 190665/1988.
Such a gasket is made in the following manner. As shown in FIGS. 8 and 9, a gasket 22 is formed by winding, in the form of a ring, a band-like steel sheet 20 and a gasket material 21 such as asbestos overlapping each other. In the gasket 22, the winding end 20A of the band-like steel sheet 20 at the outer periphery side of the gasket 22 is raised such that, when the gasket 22 is inserted into a large-diameter portion 24 of an exhaust hole 23, the winding end 20A resiliently comes in contact with the large-diameter portion 24.
In the gasket 22 having the arrangement mentioned above, when the gasket 22 is inserted into the large-diameter portion 24 of the exhaust hole 23, the winding end 20A at the outer periphery side is turned inwardly, causing the winding end 20A to resiliently come in contact with the large-diameter portion 24. Accordingly, the gasket 22 is so held as not to fall off of the exhaust hole 23 due to vibration or the like. It is therefore not necessary to support the gasket 22 by hand or with a jig until a flange portion 25A of an exhaust pipe 25 comes in contact with the gasket 22. This advantageously improves the workability of attaching of the gasket 22 and the exhaust pipe 25.
In the conventional gasket 22 mentioned above, however, there is a likelihood that a portion of the gasket 22 will protrude into the exhaust pipe 25 in a state where the gasket 22 is properly installed. If a portion of the gasket 22 protrudes into the exhaust pipe 25, the protruding portion deteriorates or is damaged, causing the sealing properties of the gasket to be decreased in a short period of time.